JP2888047B2 - Voice communication method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice communication system,
In particular, it relates to a voice communication system of a mobile satellite communication system.

[0002]

2. Description of the Related Art In a voice communication using a mobile satellite communication system, a burst signal is usually transmitted from a transmission circuit using a method called voice activation. Therefore, the transmitting circuit adds a preamble to the transmitted signal so that the receiving circuit can reproduce the reference carrier,
Furthermore, a unique word (UW) must be added so that frame synchronization can be established.

[0003] First, conventional mobile voice communication using a satellite will be described with reference to FIGS. However, it is assumed that one frame of the audio signal in FIG. 3 is further divided into N sub-frames, and voice activation starts in units of this sub-frame. Also,
The voice codec 301 in FIG. 3 encodes and digitizes an input voice signal on the transmission side, and inputs it to the transmission circuit 302 (D1). On the reception side, the reception circuit 310
Is converted into an analog audio signal and transmitted, and the voice codec 301 recognizes that there is voice data from the frame pulse F2 input from the receiving circuit 310.

[0004] The analog audio signal input to the voice codec 301 is digitized and transmitted to a transmission circuit 302. D1 input to the transmission circuit 302 is input to the voice detection circuit 303 and the preamble addition circuit 305. The voice detection circuit 303 detects the start subframe of the voice from the D1 by the activation method, and outputs the detection signal DET1 to the preamble generation circuit 3
04 and the CARR gate circuit 308. The preamble generation circuit 304 sends the preamble pattern P1 to the preamble addition circuit 305 from the input DET1.

In the preamble adding circuit 305, P1 is added to the input D1 to the transmission signal shown in FIG. 4, and in the UW adding circuit 307, U1 is added to the transmission signal shown in FIG. 308 (D2). In the CARR gate circuit 308, a CARR gate (see FIG. 4) is generated from DET1 input from the voice detection circuit 303, and D2 passes through the CARR gate. Finally, the transmission signal in the baseband band shown in FIG. Is obtained. This transmission signal is transmitted to I
The signal is modulated into an F signal and sent to an up-converter.

In the receiving circuit 310, the IF signal input from the down converter is demodulated into a base band by a demodulating circuit 311 to obtain a base band receiving signal indicated by D3 in FIG. (D3). When the demodulation circuit 311 regenerates the reference carrier, the CARR DET (CDE in FIG. 3) shown in FIG.
T) is turned on, and this is also input to the frame synchronization circuit 313. A UW detection circuit 312 is provided in the frame synchronization circuit 313. When the CDET is turned on, the UW detection circuit 312 opens the UW aperture, detects UW,
A frame pulse F2 is transmitted at a timing positioned at the beginning of voice data after UW for detecting UW,
At the position of the DET pulse, the UW aperture is closed, and frame synchronization is established. Voice codec 301
2, the position of the voice data is recognized, and the voice data of D3 is converted into analog voice and transmitted.

[0007] However, the voice codec 301 uses F2
Is recognized as voice data, and the voice data is converted into an audio signal. Therefore, the voice data from the preamble to the UW (A portion of D3 in FIG. 4) is not converted, becomes invalid, and is more effective than the B portion of D3. Becomes voice. As a result, the beginning of the output sound is cut off (this is called the beginning of the speech), and it becomes very difficult to hear.

For this reason, recently, when a preamble is added by a transmission circuit as shown in a transmission signal in FIG. 6, the preamble SOM (START-OF-MASSAG) is added.
E) is added, and the purpose of this SOM is to inform the voice codec 501 of the start position of the voice data, similarly to the UW. A transmission / reception circuit to which SOM is added is represented as shown in FIG. FIG.
3 is different from the preamble generation circuit 304 in FIG. 3 in that the preamble generation circuit 504 generates a preamble pattern by adding SOM to the preamble. The other is that the frame synchronization circuit in the reception circuit is composed of the SOM detection circuit 513 and the UW detection circuit 514 in FIG. 5, and an OR circuit 515 is added.

The IF signal input to the receiving circuit 510 is
The demodulation circuit 511 in FIG. 5 demodulates the signal into a baseband signal such as D3 in FIG. 6. The demodulation circuit 511 further reproduces the reference carrier in the preamble, and when it is completed, performs CDET (CARR DET in FIG. 6). ) Is turned on and input to the SOM detection circuit 513 and the UW detection circuit 514. The SOM detection circuit 513 and the UW detection circuit 514 open the SOM aperture and the UW aperture, respectively. When the SOM is detected by the SOM detection circuit 513, a frame pulse F2 is sent out at the timing located at the beginning of the voice data after the SOM, and the SOM DE is detected.
At the position of the pulse of T, the SOM aperture is closed. Further, when UW is detected, the frame pulse F3 is transmitted at the timing located at the head of the voice data after UW, and the UW aperture is closed at the position of the UWDET pulse, as in the detection of SOM, and frame synchronization is established. I do. Thus, since the voice codec 501 recognizes F2, the voice data immediately after the preamble does not become invalid. However, since the UW aperture is opened from the time when the CARR DET is turned on to the position of the UW DET pulse, the probability of UW error detection increases.

The problem described above also occurs when a burst extends over several frames. Normally, in a receiving circuit, frame synchronization is maintained within a certain period of time, and even if a time-out occurs, the antenna also transmits a dummy burst for correcting and correcting a deviation in the frequency and phase of the received clock, and a frame is transmitted. Keep in sync. However, in the case of mobile satellite communication, since a phenomenon such as shadowing occurs, the dummy burst may not be received by the receiving circuit.
In this case, when the next burst starts, similarly to the start of the first burst, it is necessary to reproduce the reference carrier by the preamble, detect UW or SOM, and make the voice codec recognize the head of the voice data.

[0011]

In this conventional voice communication system, an SOM is added as shown in the transmission signal of FIG. 6 in order to prevent a disconnection of the head of the talk, but when the CARR DET is turned on, the UW aperture also opens. In addition, there is a problem that the probability of UW error detection increases in voice data from SOM to UW.

This problem also occurs when a burst extends over several frames. Normally, the receiving circuit keeps frame synchronization within a certain period of time, and transmits a dummy burst for correcting the antenna and correcting the deviation of the frequency and phase of the received clock even if a timeout occurs, and Keep in sync. However, in the case of mobile satellite communication, shadowing and other phenomena occur,
This dummy burst may not be received by the receiving circuit. In this case, when the next burst starts, similarly to the start of the first burst, it is necessary to reproduce the reference carrier by the preamble, detect UW or SOM, and make the voice codec recognize the head of the voice data. was there.

An object of the present invention is to prevent the head of speech from being cut off,
By minimizing the length of the UW aperture,
The object of the present invention is to lower the probability of W error detection.

[0014]

In order to achieve the above object, the present invention relates to a voice communication system comprising a voice codec, a transmission circuit and a reception circuit, wherein the transmission circuit encodes an analog voice signal. Digital signal in which one frame is composed of N subframes (this is D1)
And a voice detection circuit for detecting the start of voice from D1 and transmitting a detection signal (this is referred to as DET1), and encoding an analog voice signal to transmit one frame pulse per frame (this is called F1). And when DET1 is input, SO detects which subframe the sound started from and sends out a detection signal (this is S1).
An M determination circuit and N SOM patterns are selected, and one of the N SOM patterns is selected by S1 and D
A preamble generating circuit for adding a preamble pattern (hereinafter, referred to as P1) to the SOM and transmitting it after a certain period of time determined when ET1 is input, and at a position determined on the frame format when D1 is input A preamble adding circuit for adding P1, and a UW for sending out a unique word (UW) pattern (hereinafter U1) after a certain time determined by F1 when F1 is input.
When the output signal of the generation circuit and the preamble addition circuit is input, U1 is placed at a position determined on the frame format.
UW addition circuit (this output is D2),
When DET1 is input, a burst gate which is turned on for the duration of the burst is generated, and CA through which D2 passes is generated.
The output signals of the RR gate circuit and the CARR gate circuit are
And a modulation circuit for modulating the F signal.

According to another aspect of the present invention, in a voice communication system including a voice codec, a transmitting circuit, and a receiving circuit, the receiving circuit synchronously detects an IF signal and demodulates the IF signal into a baseband signal. (This is D3)
When the reproduction of the reference carrier is completed, a demodulation circuit for transmitting the result to the outside (this is referred to as CDET), D3 and C3
The SOM is detected from DET, and the frame pulse (which is F
2), and decodes the SOM pattern to detect which subframe the sound started from, calculates where the UW aperture should be opened from the result, and outputs the result as a control signal (this The SOM detection circuit sends out the UW aperture at S2, detects the UW when D3 is input, and detects the UW of D3.
A UW detection circuit for transmitting a frame pulse located at the head of the data immediately after the F2 (hereinafter referred to as F3);
And an OR circuit that takes the logical sum of F3.

[0016]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing the timing of frames and signals used in FIG. 1 and 2,
One frame of the audio signal is further divided into N sub-frames, and voice activation starts in units of the sub-frames. On the transmitting side, the voice codec 101 encodes the input voice signal, digitizes the input voice signal, and inputs it to the transmitting circuit 102 (D
1) On the receiving side, the signal D3 input from the receiving circuit 111 is converted into an analog voice signal and transmitted, and the voice codec 101 recognizes that there is voice data from the frame pulse F4 input from the receiving circuit 111. It shall be.

The analog audio signal input to voice codec 101 is digitized and output to transmission circuit 102. D1 input to the transmission circuit 102 is input to the voice detection circuit 103 and the preamble addition circuit 106. The voice detection circuit 103 detects the start subframe of the voice from the D1 by the voice activation method, and sends the detection signal DET1 to the preamble generation circuit 104 and the CARR gate circuit 109. Further, the SOM determination circuit 105 determines from which of the sub-frames the voice has started based on the input frame pulse F1 and DET1, and inputs the result to the preamble generation circuit 104 (S1). Preamble generation circuit 10
4 inputs the preamble pattern P1 to which the SOM indicating the start position of the voice data is added from the input DET1 to the preamble adding circuit 106. The SOM patterns added here have a one-to-one relationship with the subframes (for example, if there are N subframes, there are N SOM patterns), and depending on the value of S1, those SOM patterns Any one of the SOM patterns is selected and added to P1. F1 is the UW generation circuit 107
Is input to the UW generation circuit 107.
The UW pattern U1 is always transmitted to the UW addition circuit 108 at a predetermined timing.

In the preamble adding circuit 106, P1 is added to the input D1 at the position indicated by the dotted line of the transmission signal in FIG.
Is added to the position indicated by the dotted line of the transmission signal in FIG. 2 and sent to the CARR gate circuit 109 (D2). In the CARR gate circuit 109, the CARR gate (FIG. 2) is turned on by DET1 input from the voice detection circuit 103,
2 passes through this, and finally a baseband transmission signal shown in the transmission signal in FIG. 2 is obtained. This transmission signal is modulated by a modulation circuit 110 into an IF signal and output to an up-converter.

In the receiving circuit 111, the IF signal input from the down converter is demodulated into a baseband band by a demodulation circuit 112, and a baseband band reception signal indicated by D3 in FIG. It is input (D3). When the demodulation circuit 112 regenerates the reference carrier, the CARR DET (CDE in FIG. 1) shown in FIG.
T), which is also input to the frame synchronization circuit 113. The frame synchronization circuit 113 includes the SOM detection circuit 11
4 and a UW detection circuit 115. In the SOM detection circuit 114, upon receiving CDET, the SOM shown in FIG.
Open the aperture, detect the SOM in D3, and
Is detected, the frame pulse F2 is sent out at the timing located at the beginning of the voice data after the SOM, and FIG.
The SOM aperture is closed at the position of the SOMMET pulse shown in FIG. As described above, the SOM pattern used in this embodiment is determined by the subframe at the start of the sound.
Since the M pattern changes, in the SOM detection circuit 114,
After the SOM is detected, the subframe of the voice start is determined,
The position of the next UW is calculated, and the control signal is given to the UW detection circuit 115 (S2). The UW detection circuit 115 opens the UW aperture shown in FIG. 2 at the position designated by S2, detects UW, and when UW is detected, similarly to the SOM detection circuit 114, sets the position at the beginning of the voice data after UW. The frame pulse F3 is output at the timing
At the UW DET pulse position shown in FIG. 2, the UW aperture is closed, and frame synchronization is established. F2 and F3 are input to the OR circuit 116, and a frame pulse like F4 is obtained. The voice codec 101 recognizes the position of the voice data from F4, converts the voice data of D3 into analog voice, and outputs it.

When the burst extends over several frames, the position of the UW aperture is set to the same position as that of the first frame from the second frame, and F4 is generated only by UW detection.
Establish frame synchronization. As a result, the head disconnection can be prevented, and the probability of UW error detection can be reduced.

[0022]

As described above, according to the present invention, the SOM depends on which sub-frame the speech starts from.
In order to change the pattern, the position of UW can be calculated by detecting the SOM in the receiving circuit.
By preventing the head of speech from being cut off and minimizing the length of the UW aperture, there is an effect that the probability of UW error detection can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a diagram showing timings of frames and signals used in one embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a conventional voice communication system.

FIG. 4 is a diagram showing timings of frames and signals used in an example of a conventional voice communication system.

FIG. 5 is a block diagram showing another example of the conventional voice communication system.

FIG. 6 is a diagram showing timings of frames and signals used in another example of the conventional voice communication system.

[Explanation of symbols]

 Reference Signs List 101 voice codec 102 transmission circuit 103 voice detection circuit 104 preamble generation circuit 105 SOM determination circuit 106 preamble addition circuit 107 UW generation circuit 108 UW addition circuit 109 CARR gate circuit 110 modulation circuit 111 reception circuit 112 demodulation circuit 113 frame synchronization circuit 114 SOM detection Circuit 115 UW detection circuit 116 OR circuit

Claims (2)

(57) [Claims] In a voice communication system including a voice codec, a transmission circuit, and a reception circuit, a transmission circuit encodes an analog voice signal so that one frame is composed of N subframes and is converted into a digital signal (D1). ), And a voice detection circuit for detecting the start of voice from D1 and transmitting a detection signal (this is referred to as DET1), encoding an analog voice signal and transmitting one transmission frame pulse ( When DET1 is input, SOM detects which subframe the voice started from and sends out a detection signal (this is S1).
A decision circuit, having N SOM patterns, selecting one of the N SOM patterns by S1 and
After a certain period of time determined when T1 is input, a preamble pattern (referred to as P1) is added to the SOM and transmitted, and when D1 is input, a preamble generating circuit is located at a position determined on the frame format. A preamble adding circuit for adding P1;
UW which sends out a unique word (UW) pattern (this is referred to as U1) after a certain period of time determined by 1.
When the output signal of the generation circuit and the preamble addition circuit is input, U1 is placed at a position determined on the frame format.
UW addition circuit (this output is D2),
When DET1 is input, a burst gate which is turned on for the duration of the burst is generated, and CA through which D2 passes is generated.
The output signals of the RR gate circuit and the CARR gate circuit are
And a modulation circuit for modulating the F signal. 2. A voice communication system comprising a voice codec, a transmission circuit, and a reception circuit, wherein the reception circuit synchronously detects an IF signal and demodulates the IF signal into a signal in a baseband (this is converted to D3
And a demodulation circuit for transmitting the result to the outside when the reproduction of the reference carrier is completed (this is referred to as CDET);
SOM is detected from D3 and CDET, and a frame pulse (referred to as F2) located at the head of the data immediately after the preamble of D3 is transmitted. Further, the SOM pattern is decoded to determine from which subframe the voice started. And a SOM detection circuit that calculates where the UW aperture should be opened from the result and sends the result as a control signal (this is referred to as S2).
When the W aperture is opened and D3 is input, a UW detection circuit for detecting UW and sending out a frame pulse (this is F3) located at the head of the data immediately following the UW of D3, and a logical sum of F2 and F3 And an OR circuit which takes the following.